Character and video mode control circuit
US4613856A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 4, 1983 |
| Grant date | Sep 23, 1986 |
| Priority date | — |
| Expiry date | Apr 4, 2003 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG09G5/222
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An electrical circuit is described that requires a reduced number of data bits for character-address and video-mode information by using a predetermined bit combination of the video-mode information as part of the character-address information. Character-address and video-mode information is output from a random access memory (RAM) to a character read only memory (ROM) and a video-mode detection circuit that produces outputs to enable video-mode circuits in the video control circuitry. One output of the video-mode detection circuit is coupled to an address input of the character ROM that has characters divided into two character sets. A predetermined bit combination of the video-mode information produces an output from the video-mode detection circuit that selects one of the character sets while the other bit combinations produce an output from the detection circuit that selects the other character set. In this way, character-address and video-mode information having n data bits can produce character and video-mode outputs that normally require n+1 data bits.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.